Dual-mode data carrier and circuit for such a data carrier with improved mode change-over

ABSTRACT

A data carrier ( 1 ) which can be operated in a contact-bound mode and in a contactless mode and a circuit ( 1 A) for such a data carrier ( 1 ) has a.c. detection means ( 69 ) for detecting the presence of a useful HF signal (HF) received via a transmission coil ( 31 ) and clock signal detection means ( 73 ) for detecting a clock signal (CLK 1 ) received via a transmission contact ( 16 ), and has logic means ( 82 ) which cooperate with the a.c. detection means ( 69 ) and the clock signal detection means ( 73 ) and which enable the activation of the contact-bound mode (CONTACT) and the activation of the contactless mode (CONTACTLESS) to be initiated.

BACKGROUND OF THE INVENTION

The invention relates to a data carrier which can be operated in acontact-bound mode and in a contactless mode and which includes themeans specified hereinafter, namely transmission contacts which aremechanically accessible from outside the data carrier and of which afirst transmission contact serves to receive a clock signal in thecontact-bound mode of the data carrier, and at least one transmissioncoil which is inductively accessible from outside the data carrier andwhich serves to receive a useful HF signal in the contactless mode ofthe data carrier, and a circuit which includes a.c. detection meansconstructed to detect the presence of a received useful HF signal, bywhich a.c. detection means the supply of contactless activationinformation can be initiated upon the detection of the presence of sucha useful HF signal in a detection process, which information enables thecontactless mode to be activated.

The invention further relates to a circuit for a data carrier which canbe operated in a contact-bound mode and in a contactless mode and whichincludes the means specified hereinafter, namely contact terminals whichare adapted to be connected to transmission contacts which aremechanically accessible from outside a data carrier and of which a firstcontact terminal serves to receive a clock signal in the contact-boundmode of the circuit, and two coil terminals which serve for connectionto a transmission coil which is inductively accessible from outside adata carrier and for receiving a useful HF signal in the contactlessmode of the circuit, and a.c. detection means constructed to detect thepresence of a received useful HF signal, by which a.c. detection meansthe supply of contactless activation information can be initiated uponthe detection of the presence of such a useful HF signal a detectionprocess, which information enables the contactless mode to be activated.

Such a data carrier of the type defined in the first paragraph and sucha circuit of the type defined in the second paragraph are known, forexample from the document WO 96/38814 A1.

The known data carrier includes only the a.c. detection means, which inthis case are realized by an a.c. detection circuit which is connecteddirectly to a transmission coil and which activates the contactless modeand thus a contactless interface when a useful HF signal appears acrossthe transmission coil. A problem encountered with the known data carrieris that in an operating condition in which the data carrier is in thecontact-bound mode and powerful spurious signals are received via thetransmission coil the received spurious signals fake a received usefulHF signal, which is detected as the appearance of a useful HF signal bythe a.c. detection circuit, as a result of which in response to thereceived spurious signal the contactless mode is activated erroneously,although the data carrier has been set to and should remain in thecontact-bound mode. Thus, in the case of the known data carrier theoperation in the contact-bound mode is interrupted, in response to aspurious signal received by means of the transmission coil, which in thecase that a data transmission process is in progress in thecontact-bound mode results in this process being disrupted. Such aninterruption or disruption of an activated mode of operation as a resultof an undesired activation of the other mode of operation is obviouslyundesirable and inadmissible.

SUMMARY OF THE INVENTION

It is an object of the invention to preclude the afore-mentioned problemand to provide an improved data carrier and an improved circuit for adata carrier in a simple manner and with the aid of simple means.

According to the invention, in order to achieve the afore-mentionedobject in a data carrier of the type defined in the first paragraph, thecircuit in addition includes clock signal detection means connected to afirst contact terminal of the circuit, which contact terminal isconnected to the first transmission contact, which clock signaldetection means are constructed to detect the presence of a receivedclock signal and upon the detection of the presence of such a clocksignal in a detection process enable the supply of contact-boundactivation information to be initiated by means of which thecontact-bound mode can be activated, and the circuit includes logicmeans arranged to receive the contactless activation information and thecontact-bound activation information and constructed so as to supplycontactless mode-setting information associated with said contactlessactivation information when solely the contactless activationinformation occurs and to supply contact-bound mode-setting informationassociated with said contact-bound activation information when solelelythe contact-bound activation information occurs and to give one of thetwo types of activation information priority over the other one of thesetwo types of activation information when these two types of activationinformation occur simultaneously and accordingly supply the mode-settinginformation associated with the activation information having priority,the contact-bound mode-setting information enabling the contact-boundmode and the contactless mode-setting information enabling thecontactless mode of the data carrier to be set. In this way it isassured with only a minimal additional expenditure that a data carrierin accordance with the invention is always set to the correct anddesired mode and that it can be excluded that while the desired mode isactive the other non-desired mode can be activated inadvertently byspurious effects or other negative influences. Thus, a very highreliability is guaranteed as regards the activation of the desired modeof operation in the data carrier in accordance with the invention.

In a data carrier in accordance with the invention having thecharacteristic features defined in the independent claim 1 the logicmeans can advantageously be constructed in such a manner that the logicmeans are advantageously adapted to give the contact-bound activationinformation priority over the contactless activation information and,accordingly, to supply the associated contact-bound mode-settinginformation in the case of a simultaneous occurrence of the contactlessactivation information and the contact-bound activation information,which results in the contactless mode being activated. This guarantees ahigh reliability of the data carrier as regards the activation andmaintenance of the contactless mode. In a data carrier in accordancewith the invention having the characteristic features defined in theindependent claim 1 it has also proved to be advantageous if, inaddition, the measures defined in the dependent claim 2 are taken. Thisguarantees a high reliability of the data carrier as regards theactivation and maintenance of the contact-bound mode.

In a data carrier in accordance with the invention having thecharacteristic features defined in the independent claim 1 it has alsoproved to be advantageous if, in addition, the measures defined in thedependent claim 3 are taken. This guarantees a particularly highreliability of the data carrier as regards the activation andmaintenance of the contact-bound mode. It is to be noted that themeasures defined in the dependent claim 3 can also be appliedadvantageously to a data carrier in accordance with the invention havingthe characteristic features defined in the dependent claim 2.

With regard to a data carrier having supply potential detection meansreference is also made to the document EP 0 424 726 B1. Said documentdiscloses a data carrier which includes a discriminator circuit assupply potential detection means, which circuit has a firstdiscriminator input and a second discriminator input, the firstdiscriminator input being arranged to receive a first directvoltage—obtained by rectification and smoothing of an alternatingvoltage induced in two transmission coils—and the second discriminatorinput being arranged to receive a second direct voltage—applied to thedata carrier via two transmission contacts—and the discriminator circuitproducing on its output a signal which has two different logic levelsdepending on the presence of the first direct voltage or the seconddirect voltage, each of levels corresponding to one of the two possiblemodes of operation. To activate the two possible modes of this knowndata carrier it is necessary to detect the presence of two directvoltages. The problem which then arises is that the second directvoltage received from the transmission contacts can be invalidated, forexample by electrostatic effects, as is possible for example as a resultof the transmission contacts being touched. Furthermore, the firstdirect voltage received from the transmission coil can be invalidated,for example, by spurious electromagnetic radiation. Both invalidationsmay lead to an erroneous discrimination by means of the discriminatorcircuit, which may result in an active mode being left inadvertently orin constant switching over between the two possible modes of operationof the known data carrier. On the other hand, in a data carrier inaccordance with the invention as described hereinbefore additionalsupply potential detection means monitor the occurrence and the presenceof a received useful HF signal, a received clock signal and a receivedfirst supply potential, which almost surely precludes an undesiredquitting of an activated mode or an undesired continual switchingbetween the two possible modes of operation of the data carrier inaccordance with the invention.

In a data carrier in accordance with the invention having thecharacteristic features defined in the dependent claim 3 it has provedto be advantageous if, in addition, the measures defined in thedependent claim 4 are taken. This is advantageous in view of a simpleimplementation of the circuit, particularly when the circuit isimplemented in the form of an integrated circuit.

In a data carrier in accordance with the invention having thecharacteristic features defined in the dependent claim 4 it has provedto be advantageous if, in addition, the measures defined in thedependent claim 5 are taken. This guarantees that the contact-bound moderemains active even if after a simultaneous occurrence and detection ofa clock signal and a first supply potential the contact-bound mode isactivated in this data carrier in accordance with the invention andsubsequently the occurrence of the clock signal is interrupted.Moreover, it is thus guaranteed that even if a spurious potential whichsimulates the presence of a first supply potential appears on the secondtransmission contact of this data carrier in accordance with theinvention while the contactless mode is active in the data carrier thecontactless mode cannot be interrupted.

In a data carrier in accordance with the invention having thecharacteristic features defined in the dependent claim 5 it has provedto be advantageous if, in addition, the measures defined in thedependent claim 6 are taken. This has also proved to be veryadvantageous in view of a simple implementation of the circuit,particularly when the circuit is implemented in the form of anintegrated circuit.

According to the invention, in order to achieve the afore-mentionedobject, a circuit of the type defined in the second paragraph ischaracterized in that the circuit in addition includes clock signaldetection means connected to a first contact terminal of the circuit,which contact terminal can be connected to a first transmission contactof a data carrier, which clock signal detection means are constructed todetect the presence of a received clock signal and upon the detection ofthe presence of such a clock signal in a detection process enable thesupply of contact-bound activation information to be initiated by meansof which the contact-bound mode can be activated, and the circuitincludes logic means arranged to receive the contactless activationinformation and the contact-bound activation information and constructedso as to supply contactless mode-setting information associated withsaid contactless activation information when solely the contactlessactivation information occurs and to supply contact-bound mode-settinginformation associated with said contact-bound activation informationwhen solely the contact-bound activation information occurs and to giveone of the two types of activation information priority over the otherone of these two types of activation information when these two types ofactivation information occur simultaneously and, accordingly, to supplythe mode-setting information associated with the activation informationhaving priority, the contact-bound mode-setting information enabling thecontact-bound mode and the contactless mode-setting information enablingthe contactless mode of the circuit to be set. In this way, advantageswhich correspond to the advantages described hereinbefore for a datacarrier in accordance with the invention having the characteristicfeatures defined in the independent claim 1 are obtained for a circuitin accordance with the invention.

The advantageous variants of a circuit in accordance with the invention,which variants have the characteristic features defined in the dependentclaims 8 to 12, yield advantages which correspond to the advantagesdescribed above for the advantageous variants of a data carrier inaccordance with the invention, which variants have the characteristicfeatures defined in the dependent claim defined in the dependent claims2 to 6.

The afore-mentioned aspects as well as further aspects of the inventionwill be apparent from the embodiments described hereinafter by way ofexamples and will be elucidated with reference to this embodiments.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be described in more detail with reference to twoembodiments shown in the drawings and given by way of examples, but towhich the invention is not limited.

FIG. 1 is a diagrammatic representation in the form of a block diagramwhich shows the relevant part of a data carrier and a circuit for thisdata carrier in accordance with a first embodiment of the invention.

FIG. 2 is a truth table for signals and information which can occur inthe data carrier and the circuit shown in FIG. 1.

FIG. 3 is another truth table for signals and information which canoccur in the data carrier and the circuit shown in FIG. 1.

FIG. 4, in the same way as FIG. 1, shows a data carrier and a circuitfor this data carrier in accordance with second embodiment of theinvention.

FIG. 5 is a truth table for signals and information which can occur inthe data carrier and the circuit shown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a diagrammatic representation in the form of a block diagramwhich shows a part of a data carrier 1 and a circuit 1A for the datacarrier 1 in accordance with a first embodiment of the invention. In thepresent case the data carrier 1 is a so-called combi-card. The circuit1A is an integrated circuit. The data carrier 1 and its circuit 1A canbe operated in a so-called contact-bound mode and in a so-calledcontactless mode.

The data carrier 1, i.e. its circuit 1A, includes a microcomputer 2,which performs a plurality of functions and tasks. The microcomputer 2serves inter alia for the processing of data which it receives orsupplies. The microcomputer 2 has a potential terminal 3 for receiving asupply potential VDD or VCC, a clock signal terminal 4 for receiving aclock signal CLK1 or CLK2, a control terminal 5 for receivingmode-setting information KBEI or KLEI, a first data port 6 for seriallyreceiving and serially supplying useful data D-KB when the contact-boundmode is active, a second data port 7, which comprises a plurality ofterminals and which serves for the parallel reception and the parallelsupply of useful data D-KL when the contactless mode is active, and athird data port 8 for supplying and for receiving useful data D-KB inthe contact-bound mode as well as useful data D-KL in the contactlessmode.

Connected to the third data port 8 of the microcomputer 2 are memorymeans 9 which include a RAM 10 forming the working memory, a ROM 11forming the program memory, and an EEPROM 12 forming a program memoryand data memory. The memory means 9 have a potential terminal 13 forreceiving a supply potential VDD or VCC and a data port 14 for receivingand supplying useful data D-KB or D-KL. The data port 14 is connected tothe third data port 8 of the microcomputer 2.

The data carrier 1 basically serves for processing useful data D-KBtransmitted by a suitable transmitting/receiving device and received bythe carrier in its contact-bound mode by means of the microcomputer 2and subsequently storing this data in the memory means 9, or readinguseful data D-KB from the memory means 9 by means of the microcomputer 2and subsequently transferring this data to a suitabletransmitting/receiving device which cooperates with the data carrier 1.Furthermore, the data carrier 1 serves for processing useful data D-KLsupplied by a suitable transmitting/receiving device and inductivelytransmitted to the data carrier 1 in its contactless mode by means ofthe microcomputer 2 and for storing this data in the memory means 9, orreading useful data D-KL from the memory means 9 by means of themicrocomputer 2 and subsequently processing this data and transmittingthe data inductively to a suitable transmitting/receiving device.

The data carrier 1 has a contact array 15 which in the present casecomprises a eight transmission contacts 16, 17, 18, 19, 20, 21, 22 and23 in total. In the present case these eight transmission contacts 16 to23 are formed by contact pads whose flat shapes are shown onlydiagrammatically in FIG. 1. The transmission contacts 16 to 23 formed bycontact pads are mechanically accessible from outside the data carrier1. In other words, this means that these transmission contacts 16 to 23are engageable with mating contacts of a suitable transmitting/receivingdevice when the data carrier 1 is introduced into thistransmitting/receiving device.

The contact array 15 has a first transmission contact 16 which servesfor receiving a clock signal CLK1 in the contact-bound mode of the datacarrier 1. The contact array 15 further has a second transmissioncontact 17 which serves for receiving a first supply potential VCC inthe contact-bound mode. The contact array 15 further has a thirdtransmission contact 18 which serves for receiving a second supplypotential in the contact-bound mode, which supply potential in thepresent case is ground potential, as is indicated in FIG. 1. The contactarray 15 further has a fourth transmission contact 19 which serves fortransferring useful data D-KB, i.e. via which the useful data D-KBsupplied by a suitable transmitting/receiving device can be supplied tothe data carrier 1 and via which useful data D-KB supplied by the datacarrier 1 can be applied to a transmitting/receiving device. The contactarray 15 further has a fifth transmission contact 20 which serves forreceiving a reset signal (RST). Since the use and effect of such a resetsignal is not relevant in the present context this is not discussed anyfurther with reference to FIG. 1. The contact array 15 further has asixth transmission contact 21, a seventh transmission contact 22 and aneighth transmission contact 23. These three transmission contacts 21, 22and 23 are free, i.e. not used, in the present data carrier 1.

The first transmission contact 16 is connected to a first contactterminal 16A of the circuit 1A, which terminal is connected to anelectrically conductive clock signal line 24, via which a clock signalCLK1, supplied via the first transmission contact 16 and the firstcontact terminal 16A, can be applied to a first input terminal 25 ofcontrollable clock signal switching means 26. The clock signal switchingmeans 26 have a potential terminal 99 for receiving a supply potentialVDD or VCC and an output 27, which output is connected to the clocksignal terminal 4 of the microcomputer 2 and via which the clock signalCLK1 and a further clock signal CLK2 can be applied to the microcomputer2. In order to be controlled, the controllable clock signal switchingmeans 26 have a control input 68, to which mode-setting information KBEIor KLEI can be applied.

The second transmission contact 17 is connected to a second contactterminal 17A of the circuit 1A, which terminal is connected to a firstelectrically conductive potential line 28, via which the first supplypotential VCC can be applied to various circuit sections of the datacarrier 1, i.e. of the circuit 1A of the data carrier 1, as will bedescribed hereinafter.

The third transmission contact 18 is connected to a third contactterminal 18A of the circuit 1A, which terminal is connected to a secondelectrically conductive potential line 29, via which the groundpotential can be applied to various circuit sections of the data carrier1, i.e. of the circuit 1A of the data carrier 1, which is not shown inFIG. 1 for the sake of the clarity of the drawing.

The fourth transmission contact 19 is connected to a fourth contactterminal 19A of the circuit 1A, which terminal is connected to anelectrically conductive data line 30, via which the fourth contactterminal 19A is connected to the first data port 6 of the microcomputer2, as a result of which useful data D-KB can be transferred between thefourth transmission contact 19 and the first data port 6 of themicrocomputer 2 via this data line 30 when the data carrier 1, i.e. thecircuit 1A, is active in the contact-bound mode.

As regards the transmission contacts 16 to 23 of the contact array 15 itis to be noted that as a result of a supply potential VDD generated inthe circuit 1A of the data carrier 1 in the contactless mode of the datacarrier 1, i.e. of the circuit 1A, a potential can appear on at leastone transmission contact and one further transmission contact, whichpotential is produced via internal circuit sections, such as for exampledriver stages for energizing the transmission contacts and which can beinfluenced from outside the data carrier 1. A d.c. potential of a givenpotential value, i.e. the potential value of the supply potential VDD,can also appear on the fourth transmission contact 19. Without specialarrangements and measures the data carrier 1 would have the problem thatdifferent potential values could appear on various contacts, as a resultof which touching of the various contacts, for example the twotransmission contacts 17 and 18 or the two transmission contacts 19 and18, with a coin or any other electrically conductive object would leadto a short-circuit of the different potential values, which is notdesirable. For this reason, the data carrier 1 shown in FIG. 1 has beenprovided with additional means in order to preclude the afore-mentionedproblem, which will be described in more detail hereinafter.

The data carrier 1 further has a transmission coil 31 incorporated inthe data carrier 1, which coil is inductively accessible from outsidethe data carrier 1 and serves for receiving a useful HF signal HF from asuitable transmitting/receiving device in the contactless mode of thedata carrier 1. Such a useful HF signal HF can be received by the datacarrier 1 when the data carrier 1 is within the range of such atransmitting/receiving device. In addition to the contact-bound modecommunication possibility via the contact array 15 the transmission coil15 also provides the possibility of communication between the datacarrier 1 and a suitable transmitting/receiving device by an inductivemethod.

The transmission coil 31 of the data carrier 1 has two coil ends 32 and3. The two coil ends 32 and 33 are connected to two coil terminals 32Aand 33A of the circuit 1A of the data carrier 1, which coil terminalsare connected to processing means 34 shown in dash-dot lines in FIG. 1.

The processing means 34 comprise rectifier means 35 as supply voltagegenerating means, transfer means 36, clock signal regenerating means 37,demodulator means 38 and modulator means 39. In a manner not shown, theafore-mentioned means 35 to 39 are connected to the coil terminals 32Aand 33A and, consequently, to the transmission coil 31 via the coil ends32 and 33. The processing means 34 have a potential terminal 40 to whicha supply potential VCC or VDD can be applied. A supply potential VCC orVDD applied to the potential terminal 40 can be supplied to the means 35to 39 in a manner not shown. The potential terminal 40 is connected to asecond electrically conductive potential line 41.

The rectifier means 35 serve for rectifying a useful HF signal HFreceived from the transmission coil 31. When the rectifier means 35receive such a useful HF signal HF the rectifier means 35 generate asupply voltage and thus a second supply potential VDD, which is appliedto the second electrically conductive potential line 41 via anelectrically conductive line 42.

The transfer means 36 serve for transferring an useful HF signal HFreceived by the transmission coil 31 and applied to the transfer means36. The transfer means 36 supply a useful HF signal HF applied to themto a further electrically conductive line 43.

The clock signal regenerating means 37 serve for regenerating a clocksignal CLK2, which the clock signal regenerating means 37 derive from auseful HF signal HF received by means of the transmission coil 31 andapplied to the clock signal regenerating means 37. The clock signalregenerating means 37 supply a clock signal CLK2 regenerated by saidmeans to a further electrically conductive line 44, which leads to asecond input terminal 45 of the clock signal switching means 26, thusenabling a regenerated clock signal CLK2 to be applied to the clocksignal terminal 4 of the microcomputer 2 via the clock signal switchingmeans 26.

The demodulator means 38 serve for and are constructed for demodulatinga useful HF signal HF received by means of the transmission coil 31 andapplied from this coil to the demodulator means 38, which demodulatormeans 38 enable useful data D-KL conveyed by a received useful HF signalHF as a modulation to be derived from the received useful HF signal HF.The demodulator means 38 supply the useful data D-KL which they havederived to a further electrically conductive line 45.

The modulator means 39 serve to modulate useful data D-KL, which can beapplied to the modulator means 39 via a further electrically conductiveline 46 and which, after they have been modulated, can be applied fromthe modulator means 39 to the transmission coil 31 in order to betransmitted to a suitable transmitting/receiving device constructed forinductive transmission. The modulator means 39 have a control input 47connected to a further electrically conductive line 48 via which anenable signal can be applied to the modulator means 39.

The electrically conductive lines 45, 46 and 48 are connected toterminals 49, 50 and 51 of first controllable decoupling means 52. Thefirst controllable decoupling means 52 have a potential terminal 53, viawhich a supply potential VCC or VDD can be applied to the firstcontrollable decoupling means 52. The first controllable decouplingmeans 52 further have a control input 54 via which mode-settinginformation KBEI or KLEI can be applied to the first controllabledecoupling means 52. The first controllable decoupling means furtherhave a serial data port 55 connected to a first serial data port 57 ofdata processing means 58 via a first bidirectional serial data line 56.

The data processing means 58 comprise a hard-wired circuit device bymeans of which useful data D-KL received by the data carrier 1 can beprocessed before being applied to the microcomputer 2 and by means ofwhich useful data D-KL supplied by the microcomputer 2 can be processedbefore being transmitted by the transmission coil 31. The dataprocessing means 58 have a potential terminal 59, to which a supplypotential VCC or VDD can be applied. The data processing means 58further have a second serial data port 60 connected to a serial dataport 62 of second controllable decoupling means 63 via a second serialdata line 61.

The second controllable decoupling means 63 have a potential terminal 64via which a supply potential VCC or VDD can be applied to the secondcontrollable decoupling means 63. The second controllable decouplingmeans 63 further have a control input 65 via which mode-settinginformation KBEI or KLEI can be applied to the second controllabledecoupling means 63. The second controllable decoupling means 63 furtherhave a parallel data port 66 comprising a plurality of separateterminals and connected to the second data port 7 of the microcomputer 2via a parallel data bus 67. The parallel data bus 67 enables atransmission of useful data D-KL in parallel form between the secondcontrollable decoupling means 63 and the microcomputer 2.

The first controllable decoupling means 52 serve to decouple, on the onehand, the demodulator means 38 and the modulator means and, on the otherhand, the data processing means 58 and the second controllabledecoupling means 63 serve to decouple, on the one hand, the dataprocessing means 58 and, on the other hand, the microcomputer 2. Thecontrollable decoupling means 52 and 53 are controllable via the controlinputs 54 and 65 in such a manner that the controllable decoupling means52 and 63 can each be switched between a decoupling state and a couplingstate. When the controllable decoupling means 52 and 63 are each in thecoupling state a data transfer of useful data D-KL from the transmissioncoil 31 to the microcomputer 2 and finally from the latter to the memorymeans 9 is possible via the demodulator means 38, the first decouplingmeans 52, the data processing means 58 and the second decoupling means63 and, in the opposite direction, a data transfer of useful data D-KLis possible from the memory means 9 to the transmission coil 31 via themicrocomputer 2, the second decoupling means 63, the data processingmeans 58, the first decoupling means 52 and the modulator means 39.

The data carrier 1, i.e. its circuit 1A, includes a.c. detection means69 having an input terminal 70 connected to the electrically conductiveline 43, which thus provides an electrically conductive connectionbetween the transfer means 36 and the a.c. detection means 69. The a.c.detection means 69 have a potential terminal 71 via which a supplypotential VCC or VDD can be applied to the a.c. detection means 69. Thea.c. detection means 69 are constructed to detect the presence of areceived useful HF signal HF. Upon detection of the presence of such auseful HF signal HF in a detection process the a.c. detection means 69can initiate the supply of contactless activation information KLAI. Bymeans of such contactless activation information KLAI the contactlessmode of the data carrier 1, i.e. its circuit 1A, can be activated. It isto be noted that the a.c. detection means 69 effect a detection of thepresence of a received useful HF signal HF both when they are energizedwith the first supply potential VCC and when they are energized with thesecond supply potential VDD, which in other words means that the a.c.detection means are not capable of making a distinction between thefirst supply potential VCC and the second supply potential VDD, i.e. arenot capable of identifying or detecting at least one of the two supplypotentials VCC and VDD.

The data carrier 1 and its circuit 1A now advantageously also includecombination detection means 73.

In the present case the combination detection means 73 constitute firstclock signal detection means connected to the first contact terminal 16Aof the circuit 1A and thus to the first transmission contact 16 of thedata carrier 1 via the electrically conductive line 24, whichelectrically conductive line 24 leads to a first input terminal 74 ofthe combination detection means 73. The combination detection means 73,i.e. their part forming clock signal detection means, are constructed todetect the presence of a clock signal CLK1 received via the firsttransmission contact 16 and the first contact terminal 16A and, upondetection of the presence of such a clock signal CLK1 in a detectionprocess, the combination detection means 73 can initiate the supply ofcontact-bound activation information KBAI by means of which thecontact-bound mode can be activated.

The combination detection means 73 further form supply potentialdetection means which are connected to the second contact terminal 17Aof the circuit 1A and to the second transmission contact 17 of the datacarrier 1 via the first electrically conductive potential line 28. As isapparent from FIG. 1, the combination detection means 73 have apotential terminal 75 connected to the second contact terminal 17A andthe second transmission contact 17 via the first electrically conductivepotential line 28, thus enabling the first supply potential VCC to beapplied to the combination detection means 73 to provide the powersupply for said means. The combination detection means 73 further have apotential input terminal 105, which constitutes an identification ordetection input and which is also connected to the potential line 28,thus enabling the first supply potential VCC to be applied to thecombination detection means 73 for identification or detection purposes.The combination detection means 73, i.e. the part forming the supplypotential detection means, are constructed to detect the presence of areceived first supply potential VCC and upon detection of the presenceof such a first supply potential VCC in a detection process thecombination detection means 73 can initiate the supply of contact-boundactivation information.

In the present case of the data carrier 1 and its circuit 1A shown inFIG. 1 the combination detection means 73 are constructed in such amanner that in a detection process the supply of contact-boundactivation information KBAI can be initiated only in the case ofsimultaneous detection of the presence of a clock signal CLK1 and thepresence of a first supply potential VCC. Such contact-bound activationinformation KBAI can be supplied to an output 76 of the combinationdetection means 73.

In the data carrier 1 of FIG. 1 the combination detection means 73cooperate with memory means 77 which, in the present case, are formed ina particularly advantageous manner by a so-called latch. The memorymeans 77 have an input 78 connected to the output 76 of the combinationdetection means 73. The memory means 77 have an output 79 connected to asecond input terminal 80 of the combination detection means 73.Contact-bound activation information KBAI supplied by the combinationdetection means 73 during a detection process can be stored by thememory means 77, which is effected in order to achieve that during adetection process prior contact-bound activation information PRIOR-KBAIsupplied by the combination detection means 73 and stored in the memorymeans 77 in a previous detection process is available. The memory means77 have a potential terminal 81 via which the first supply potential VCCcan be applied to the memory means 77.

In the data carrier 1 and its circuit 1A as shown in FIG. 1 thecombination detection means 73 are, in addition, also adapted to detectthe presence of prior contact-bound activation information PRIOR-KBAIsupplied in a previous detection process and stored in the memory means77, which information can be applied to the combination detection means73 via the second input terminal 80. During a detection process—in whichdropping out of a received clock signal CLK1 but the subsequent presenceof the first supply potential VCC and the presence of priorcontact-bound activation information PRIOR-KBAI are detected—thecombination detection means 73 maintain the supply of contact-boundactivation information KBAI.

The data carrier 1 and its circuit 1A further include logic means 82.The logic means 82 have a potential terminal 83 via which a supplypotential VCC or VDD can be applied to the logic means 82 from thesecond electrically conductive potential line 41. The logic means 82further have a first input terminal 84, a second input terminal 85, afirst output terminal 86 and a second output terminal 87. The firstinput terminal 84 of the logic means 82 is connected to the output 72 ofthe a.c. detection means 69 via a further electrically conductive line88, thus enabling contactless mode activation information KLAI to beapplied to the logic means 82. The second input terminal 85 is connectedto the output 76 of the combination detection means 73 via a furtherelectrically conductive line 89, thus enabling contact-bound modeactivation information KBAI to be applied to the logic means 82.

The logic means 82 are of such a construction that if solely contactlessmode activation information KLAI occurs they supply contactlessmode-setting information KLEI associated with said activationinformation, that if solely contact-bound activation information KBAIoccurs they supply contact-bound mode-setting information KBEIassociated with said activation information, and that if at the sametime both types of activation information KLAI and KBAI occur they givethe contact-bound activation information KBAI priority over thecontactless activation information KLAI and they consequently supply theassociated contact-bound mode-setting information KBEI. The contactlessmode-setting information KLEI and the contact-bound mode-settinginformation KBEI is supplied via the first output terminal 86 of thelogic means 82. The first output terminal 86 of the logic means 82 isconnected to a further electrically conductive line 90 via which thecontactless mode-setting information KLEI and the contact-boundmode-setting information KBEI can be applied as control information tothe various circuit sections of the data carrier 1 and the circuit 1A.It is to be born in mind that by means of the contact-bound mode-settinginformation KBEI the contact-bound mode of the data carrier 1 and bymeans of the contactless mode-setting information KLEI the contactlessmode of the data carrier 1 and the circuit 1A can be selected.

In the data carrier 1 the second transmission contact 17 and the secondcontact terminal 17A of the circuit 1A, which terminal is connected tosaid transmission contact, is connected to controllable switching means91, associated with this second transmission contact 17 and the secondcontact terminal 17A, which switching means enable the application of asecond supply potential VDD, which is available in the data carrier 1and in the circuit 1A as a result of the supply voltage generated by thesupply voltage generating means, i.e. the rectifier means 35, to thesecond transmission contact 17 and to the second contact terminal 17A tobe inhibited. In the present case the controllable switching means 91are formed by a transistor switch arranged in series with the secondtransmission contact 17 and with the second contact terminal 17A andwhich can be switched between a high-impedance and a low-impedanceswitching state. In order to enable this switching process to be carriedout the controllable switching means 91 have a control input 92connected to the second output terminal 87 of the logic means 82 via afurther electrically conductive line 93.

As already explained hereinbefore, contactless activation informationKLAI, by means of which the contactless mode can be activated, can beapplied to the logic means 82 via the first input terminal 84 of saidmeans. Contact-bound activation information KBAI, by means of which thecontact-bound mode can be activated, can be applied to the logic means82 via the second input terminal 85.

The logic means 82 are of such a construction that they can also supplyswitching-means control information and that when solely the contactlessactivation information KLAI associated with said control informationoccurs they supply switching-means opening information SAI asswitching-means control information, when solely the contact-boundactivation information KBAI occurs they supply switching-means closinginformation SEI associated with said control information asswitching-means control information, and when both types of activationinformation KLAI and KBAI occur simultaneously they give thecontact-bound activation information KBAI priority over the contactlessactivation information KLAI and, consequently, also supply theassociated switching-means closing information SEI as switching-meanscontrol information. The switching-means opening information SAI and theswitching-means closing information SEI is applied to the control input92 of the switching means 91 via the electrically conductive line 93,the switching-means opening information SAI enabling the switching means91 to be set to the switching state which inhibits the application of asupply potential VDD to the second transmission contact 17 and thesecond contact terminal 17A, and the switching-means closing informationSEI enabling the switching means 91 to be set to the switching state inwhich the application a supply potential VDD to the second transmissioncontact 17 and the second contact terminal 17A. In the switching stateof the switching means 91 which enables a supply potential VDD to beapplied to the second contact terminal 17A and the second transmissioncontact 17 it is achieved advantageously that a first supply potentialVCC received from the second transmission contact 17 can be applied tothe second electrically conductive potential line 41 via the firstelectrically conductive potential line 28 and the switching means 91, asa result of which the circuit sections of the data carrier 1 and itscircuit 1A which are energized via the second electrically conductivepotential line 41 are energized with the first supply potential VCC.

The data carrier 1 and the circuit 1A shown in FIG. 1 further includespotential equalizing means 94. By means of these potential equalizingmeans 94 the second transmission contact 17, and consequently thecontact terminal 17A, and the fourth transmission contact 19, andconsequently the fourth contact terminal 19A, can be brought atsubstantially the same potential, in the present case at the groundpotential which also appears on the third transmission contact 18 andthe third contact terminal 18A, when a sufficiently powerful useful HFsignal HF is received, from which a supply voltage and, consequently,the second supply potential VDD, can be derived by the supply voltagegenerating means, i.e. the rectifier means 35, which is specifically sowhen the data carrier 1 and the circuit 1A are in the contactless mode.

In the present case, the potential equalizing means 94 are essentiallyformed by two controllable transistor switches 95 and 96, which eachhave a control input 97 and 98, respectively. Each of the two controlinputs 97 and 98 is connected to the electrically conductive line 90, towhich the logic means supply the contactless mode-setting informationKLEI and the contact-bound mode-setting information KBEI.

In a variant of the data carrier of FIG. 1, which is not shownseparately, all the eight contacts 16 to 23 of the contact array 15 canbe brought at the same potential, which can again be ground potentialbut also another potential, such as the second supply potential VDD,with the aid of potential equalizing means 94 which comprise eightcontrollable transistor switches in total.

Hereinafter, the operation of the data carrier 1 and its circuit 1A asregards the activation of the contact-bound mode and the activation ofthe contactless mode will be described, reference being made to the twotruth tables of FIGS. 2 and 3. The truth table of FIG. 2 relates to thecombination detection means 73. The truth table of FIG. 3 relates to thea,c, detection means 69 and to the logic means 82.

The first column of the truth table of FIG. 2 indicates the presence (1)or absence (0) of the clock signal CLK1 on the first input terminal 74of the combination detection means 73. The second column of this truthtable indicates the presence (1) or absence (0) of the first supplypotential VCC on the potential terminal 75 of the combination detectionmeans 73. The third column of this truth table indicates the presence(1) or absence (0) of prior contact-bound activation informationPRIOR-KBAI on the second input terminal 80 of the combination detectionmeans 73. Finally, the fourth column of this truth table indicates thepresence (1) or absence (0) of contact-bound activation KBAI on theoutput 76 of the combination detection means 73.

The first column of the truth table of FIG. 3 indicates the presence (1)or absence (0) of a useful HF signal HF on the input terminal 70 of thea.c. detection means 69. The second column of this truth table indicatesthe presence (1) or absence (0) of contactless activation informationKLAI on the output 72 of the a.c. detection means 69 and on the firstinput terminal 84 of the logic means 82. The third column of this truthtable indicates the presence (1) or absence (0) of contact-boundactivation information KBAI on the output 76 of the combinationdetection means 73 and on the second input terminal 85 of the logicmeans 82. The fourth column of the truth table of FIG. 3 indicates thepresence of contactless mode-setting information KLEI=0 and the presenceof contact-bound mode-setting information KBEI=0 on the first outputterminal 86 of the logic means 82. The fifth column of this truth tableindicates the presence of switching-means opening information SEI=0 onthe second output terminal 87 of the logic means 82. The sixth column ofthis truth table gives the switching states of the switching means 91,“ON” being the low-impedance state and “OFF” being the high-impedancestate. The seventh column of the truth table of FIG. 3 specifies themodes (MODE) of the data carrier 1 and its circuit 1A, “CONTACTLESS”indicating the contactless mode and “CONTACT” indicating thecontact-bound mode.

It is assumed that neither the contact array 15 nor the transmissioncoil 31 of the data carrier 1 are in communication with a suitabletransmitting/receiving device. In this situation—see the first rows ofthe two truth tables in FIGS. 2 and 3—neither a clock signal CLK1 nor afirst supply potential VCC nor a useful HF signal HF appear in the datacarrier 1 and its circuit 1A. As a result of the absence of the firstsupply potential VCC the combination detection means 73 and the memorymeans 77 are not energized, so that said means do not supply anyinformation. Owing to the absence of a useful HF signal HF the rectifiermeans 35 do not supply a second supply potential VDD, as a result ofwhich the a.c. detection means 69 and the logic means 62 are neitherenergized and consequently do not supply any information.

In accordance with the second row in FIG. 2, it is assumed that by meansof its contact array 15 the data carrier 1 is subsequently brought intocommunication with a suitable transmitting/receiving device provided forthis purpose, in which situation a clock signal CLK1 is transmitted tothe data carrier 1 via the first transmission contact 16, the firstsupply potential VCC is transmitted via the second transmission contact17, and ground potential is transmitted via the third transmissioncontact 18. Consequently, the combination detection means 73 detect thepresence (1) of the clock signal CLK1 and the presence (1) of the firstsupply potential VCC, which results in the occurrence (1) of thecontact-bound activation information KBAI on the output 76 of thecombination detection means 73, which is independent of the fact whetherprior contact-bound activation information PRIOR-KBAI is present (1) ornot present (0).

In accordance with the third row in FIG. 2, it is assumed thatsubsequently—i.e. after a generation (1) of contact-bound activationinformation KBAI in accordance with the second row—the supply of theclock signal CLK1 to the first transmission contact 16 and,consequently, to the data carrier 1 is interrupted—as is effectedintentionally in the case of a correct communication in thecontact-bound mode—but that the supply (1) of the first supply potentialVCC is sustained. In this situation, the combination detection means 73detect the absence (0) of the clock signal CLK1 but they also detect thepresence (1) of the first supply potential VCC as well as the presence(1) of prior contact-bound activation information PRIOR-KBAI, as aresult of which the combination detection means 73 maintain the transferof the contact-bound activation information KBAI.

In accordance with the fourth row in FIG. 2, it is now assumed thatsubsequently—regardless of whether the combination detection means 73have detected the presence (1) or absence (0) of the clock signalCLK1—the combination detection means 73 detect the absence (0) of thefirst supply potential VCC, i.e. the supply of the first supplypotential VCC has ceased. In this case the combination detection means73—regardless of whether the presence (1) or absence (0) of priorcontact-bound activation information PRIOR-KBAI on their second inputterminal 80 is detected—respond by causing a termination (0) of thesupply of contact-bound activation information KBAI.

Finally, the situation indicated in the fifth row in FIG. 2 isdescribed, in which it is assumed that the combination detection means73 detect the absence (0) of prior contact-bound activation informationPRIOR-KBAI, which means that previously the contact-bound mode was notactive. If in such a situation the combination detection means 73 detectsolely the presence (1) of the first supply potential VCC but at thesame time the absence (0) of the clock signal CLK1, this results incontact-bound activation information KBAI not (0) being available on theoutput 76 of the combination detection means 73. This means that thecontact-bound mode cannot be activated by a spurious voltage whichappears, for example as a result of inadvertent touching, on the secondtransmission contact 17, which serves for the application of the firstsupply potential VCC, which is particularly advantageous because itguarantees that the contactless mode which is for example active in thissituation is not interrupted by an inadvertent activation of thecontact-bound mode.

The description of the operation will now be continued with reference toFIG. 3. The first row of FIG. 3 represents the previously describedinitial situation of the data carrier 1, in which the data carrier 1neither the contact array 15 nor the transmission coil 31 of the datacarrier 1 are in communication with a suitable transmitting/receivingdevice.

In accordance with the second row in FIG. 3 it is now assumed that thedata carrier 1 comes within the transmitting/receiving range of atransmitting/receiving device which can inductively communicate with thedata carrier 1. In this case a useful HF signal HF is received via thetransmission coil 31. The useful HF signal HF is applied to therectifier means 35, as a result of which the rectifier means 35 start tobuild up a supply voltage and thus the second supply potential VDD. Theuseful HF signal HF is further applied to the input terminal 70 of thea.c. detection means 69, which is adapted to detect the presence (1) ofa useful HF signal HF in a reliable manner even while the second supplypotential VDD is still building up. The detection (1) of a useful HFsignal HF results in the a.c. detection means 69 supplying contactlessactivation information KLAI to their output 72, which information isapplied to the first input terminal 84 of the logic means 82. At thesame time, the absence (0) of contact-bound activation information KBAIon the second input terminal 85 of the logic means 82 is detected as aresult of the absence (0) of a clock signal CLK1 and the absence (0) ofthe first supply potential VCC. The logic means 82 are of such aconstruction that in this operating condition they first generateswitching-means opening information SAI=1 and, a given time intervalafter this, contactless mode-setting information KLEI=0. Thus, it isachieved that the switching means 91 are set to their high-impedanceswitching state with the aid of the switching-means opening informationSAI=1 via the electrically conductive line 93 and the control input 92,and that subsequently the data carrier 1 and its circuit 1A are set tothe contactless mode with the aid of the contactless mode-settinginformation KLEI=0 via the electrically conductive line 90, thecontactless mode-setting information KLEI=0 being transferred, via theelectrically conductive line 90, to the control terminal 5 of themicrocomputer 2, to the control input 65 of the second decoupling means63, to the control input 68 of the clock-signal switching means 26, tothe control input 54 of the first decoupling means 52, and to the twocontrol inputs 97 and 98 of the transistor switches 95 and 96 of thepotential equalizing means 94. In this way, the microcomputer 2, theclock-signal switching means 26, the two decoupling means 52 and 53, aswell as the potential equalizing means 94 are set to their operatingconditions which correspond to the contactless mode.

In accordance with the third row in FIG. 3, it is assumed that—after thedata carrier 1 has inductively entered into communication with atransmitting/receiving device—this communication between the datacarrier 1 and the transmitting/receiving device is maintained.Subsequently, a useful HF signal HF is received in this situation, whosepresence (1) is detected by the a.c. detection means 69, as result ofwhich these means cause the transfer (1) of the contactless activationinformation KLAI from their output 72 to the first input terminal 84 ofthe logic means 82. As long as the logic means 82 detect the absence (0)of contact-bound activation information KBAI on their second inputterminal 85, the logic means 82 subsequently produce the contactlessmode-setting information KLEI=0 on their first output terminal 86 andthe switching-means opening information SAI=1 on their second outputterminal 87. As a consequence, the switching means 91 remain in theirhigh-impedance state and the data carrier 1 is set to the contactlessmode (CONTACTLESS).

In accordance with the fourth row in FIG. 3, it is assumed that the datacarrier 1 communicates with a suitable transmitting/receiving device bymeans of its contact array 15, as a result of which the combinationdetection means 73 produce contact-bound activation information KBAI ontheir output 76 and, consequently, the logic means 82 detect thepresence (1) of the contact-bound activation information KBAI on thesecond input terminal 85 of the logic means 82. In this situation thelogic means 82 respond in such a manner—regardless of whether thepresence (1) or absence (0) of contactless activation information KLAIon the first input terminal 84 of the logic means 82 is detected—thatthe logic means 82 in all cases give the contact-bound activationinformation KBAI priority over contactless activation information KLAIwhich may be present and therefore produce on their first outputterminal 86 contact-bound mode-setting information KBEI=1, which isassociated with the contact-bound activation information KBAI, andproduce on their second output terminal 87 switching-means closinginformation SEI=0, which is likewise associated with the contact-boundactivation information KBAI. As a result of this, the switching means 91are set to their low-impedance, turned-on state, upon which the firstsupply potential VCC is applied to the second electrically conductivepotential line 41 via the first electrically conductive potential line28 and the turned-on switching means 91, which guarantees the potentialsupply to all the circuit sections of the data carrier 1 and the circuit1A, and that the data carrier 1 and the circuit 1A are set to thecontact-bound mode (CONTACT).

Owing to the provision of the a.c. detection means 69 and the additionalprovision of the combination detection means 73 the data carrier 1 andthe circuit 1A shown in FIG. 1 guarantee a particularly high reliabilityas regards a correct and substantially interference-immune selection andactivation of one of the two modes of operation of the data carrier 1and the circuit 1A, i.e. either the contact-bound mode or thecontactless mode. The provision of the switching means 91 further hasthe advantage that in the contactless mode the supply potential VDD thengenerated cannot reach the second transmission contact 17 of the contactarray 15. Moreover, the provision of the potential equalizing means 94in the data carrier 1 guarantees that both the second transmissioncontact 17 and the fourth transmission contact 19 are at groundpotential in the contactless mode of the data carrier 1 and the circuit1A and these two transmission contacts 17 and 19 therefore have the samepotential as the third transmission contact 18 in the contactless mode,which thus precludes problems as a result of potential differencesbetween these contacts in environments with explosion hazard.

FIG. 4 shows a part of a data carrier 1 and a circuit 1A for the datacarrier 1 in accordance with a second embodiment of the invention. Thedata carrier 1 of FIG. 4 has a slightly simpler circuit 1A in comparisonwith the data carrier 1 of FIG. 1.

Instead of the combination detection means 73 the data carrier 1 and thecircuit 1A of FIG. 4 comprise only clock signal detection means 100which are adapted to detect only the presence of a clock signal CLK1received in the data carrier 1 and applied to an input 101 of the clocksignal detection means 100 via the electrically conductive line 24. Thedata carrier 1 and the circuit 1A of FIG. 4 further do not include anymemory means 77, as a result of which contact-bound activationinformation KBAI available on an output 102 of the clock signaldetection means 100 can only be applied to the second input terminal 85of the logic means 82.

Another difference between the data carrier 1 and the circuit 1A shownin FIG. 4 and the data carrier 1 and the circuit 1A shown in FIG. 1 isthat in the data carrier 1 and the circuit 1A of FIG. 4 instead ofswitching means a diode 103 is included between the first electricallyconductive potential line 28 and the second electrically conductivepotential line 41. In view of this, the logic means 82 have only oneoutput terminal 86 to which either the contact-bound mode-settinginformation KBEI=1 or the contactless mode-setting information KLEI=0 issupplied, no second output terminal being provided.

FIG. 5 shows a truth table relating to the data carrier 1 shown in FIG.4. The first row in FIG. 5 represents the initial situation of the datacarrier 1 of FIG. 4.

The second row in FIG. 5 represents the situation when a useful HFsignal HF is received. As is apparent from the second row in FIG. 5,contactless activation information KLAI is generated (1) by means of thea.c. detection means 69 when a useful HF signal HF is present (1), as aresult of which the logic means 82 generate contactless mode-settinginformation KLEI=0, in response to which the data carrier 1 and thecircuit 1A are set to the contactless mode (CONTACTLESS).

As is apparent from the third row in FIG. 5, the clock signal detectionmeans 100 detect the presence (1) of the clock signal CLK1 when a clocksignal CLK1 is received, which results in contact-bound activationinformation KBAI being supplied (1) from the clock signal detectionmeans 100 to the logic means 82. As a result of this, the logic-means 82generate and supply contact-bound mode-setting information KBEI=1, whichcauses the data carrier 1 and the circuit 1A to be set to thecontact-bound mode (CONTACT).

As is apparent from the fourth row in FIG. 5, in the case that the datacarrier 1 receives both a useful HF signal HF and a clock signal CLK1,the a.c. detection means 69 generate (1) contactless activationinformation KLAI and the clock signal detection means 100 generate (1)contact-bound activation information KBAI, both types of informationbeing applied to the logic means 82. However, in the present case thelogic means 82 give priority to the contact-bound activation informationKBAI—as is also the case for the data carrier 1 of FIG. 1 (see fourthrow in FIG. 3)—as a result of which the logic means 82 also in this caseproduce the associated contact-bound mode-setting information KBEI=1 ontheir output 86 and in this case the data carrier 1 and the circuit 1Aare set to the contact-bound mode (CONTACT).

The invention is not limited to the two embodiments of the data carrierand its circuit described hereinbefore by way of example. A data carrierin accordance with the invention need not include just one transmissioncoil but may alternatively include two or more transmission coils.Instead of a latch other memory types can be used as memory means forthe cooperation with the combination detection means. Alternatively, thelogic means can be constructed so as to give the contactless activationinformation priority over the contact-bound activation information; insuch a case it may then be advantageous that the a.c. detection meanscooperate with a latch in which prior contactless activation informationcan be stored and that by means of such stored prior contactlessactivation information it is assured that when the contactless mode,which has priority, is active it cannot be disrupted by spurious signalsvia the transmission contacts. In both data carriers describedhereinbefore the a.c. detection means are intended and constructed forthe direct detection of a useful HF signal. However, alternatively, a.c.detection means may be provided which can indirectly detect a presenceof a useful HF signal, for example in that they are intended andconstructed for the detection of the presence a clock signal derivedfrom a useful HF signal by regeneration. In contradistinction to thedata carrier shown in FIG. 1 a further data carrier may comprisecombination detection means which are intended and constructed only forthe detection of the presence of a clock signal applied via atransmission contact and for the detection of the presence of a supplypotential applied via as further transmission contact and not for thedetection of prior contact-bound activation information, in which caseit is not necessary to provide memory means which cooperate with suchcombination detection means for the storage of contact-bound activationinformation generated by the combination detection means. In the datacarriers described hereinbefore the switching means and the potentialequalizing means are both implemented by means of transistor switches;however, these means can alternatively be implemented by diode switchesor other electrically controllable switches.

What is claimed is:
 1. A data carrier operable in a contact-bound modeand in a contactless mode and which includes the means specifiedhereinafter, namely transmission contacts which are mechanicallyaccessible from outside the data carrier and of which a first atransmission contact serves to receive a clock signal in thecontact-bound mode of the data carrier, and at least one transmissioncoil which is inductively accessible from outside the data carrier andwhich serves to receive a useful HF signal in the contactless mode ofthe data carrier, and a circuit which includes an a.c. detectorconnected to detect the presence of a received useful HF signal, bywhich the a.c. detector enables the supply of contactless activationinformation upon the detection of the presence of such a useful HFsignal in a detection process, which activation information enables thecontactless mode to be activated, the circuit including clock signaldetector connected to a first contact terminal of the circuit, whichcontact terminal is connected to the first transmission contact, whichclock signal detector is connected to detect the presence of a receivedclock signal and, upon the detection of the presence of such a clocksignal in a detection process, enables the supply of contact-boundactivation information to indicate activation of the contact-bound, andthe circuit including logic means arranged to receive the contactlessactivation information and the contact-bound activation information andconstructed so as to supply contactless mode-setting informationassociated with said contactless activation information when solely thecontactless activation information occurs and to supply contact-boundmode-setting information associated with said contact-bound activationinformation when solely the contact bound activation information occursand to give one of the two types of activation information priority overthe other one of these two types of activation information when thesetwo types of activation information occur simultaneously andaccordingly, to supply the mode-setting information associated with theactivation information having priority, the contact-bound mode-settinginformation enabling the contact-bound mode and the contactlessmode-setting information enabling the contactless mode of the datacarrier to be set.
 2. A data carrier as claimed in claim 1,characterized in that the logic means are adapted to give thecontact-bound activation information priority over the contactlessactivation information and, accordingly, to supply the associatedcontact-bound mode-setting information in the case of a simultaneousoccurrence of the contactless activation information and thecontact-bound activation information.
 3. A data carrier as claimed inclaim 1, which has a second transmission contact for receiving a firstsupply potential in the contact-bound mode, characterized in that thecircuit includes supply potential detection means which are connected toa second contact terminal of the circuit, said contact terminal beingconnected to the second transmission contact, and which are constructedto detect the presence of a received first supply potential and whichenable the supply of contact-bound activation information to beinitiated upon detection of the presence of such a first supplypotential during a detection process.
 4. A data carrier as claimed inclaim 3, wherein the supply potential detection means and the clockdetector are formed by combination detection means which are arranged toreceive the first supply potential for its power supply and which areconstructed both to detect the presence of a received clock signal andto detect the presence of a received first supply potential wherein thesupply of contact-bound activation information is initiated only in thecase of a simultaneous detection of the presence of a clock signal andthe presence of a first supply potential.
 5. A data carrier as claimedin claim 4, wherein the combination detection means cooperate withmemory means capable of storing contact-bound activation informationsupplied during a detection process, and the combination detection meansare, in addition, also detects the presence of prior contact-boundactivation information supplied in a previous detection process andstored in the memory means, and the combination detection meansmaintains the supply of contact-bound activation information during adetection process in which dropping out of a received clock signal butthe subsequent presence of the first supply potential and the presenceof prior contact-bound activation information are detected.
 6. A datacarrier as claimed in claim 5, wherein the memory means are formed by alatch.
 7. A circuit for a data carrier operable in a contact-bound modeand in a contactless mode comprising, contact terminals connected totransmission contacts which are mechanically accessible from outside adata carrier and of which a first contact terminal serves to receive aclock signal in the contact-bound mode of the circuit, and two coilterminals connected to a transmission coil which is inductivelyaccessible from outside a data carrier and for receiving a useful HFsignal in the contactless mode of the circuit, and a.c. detection meansconstructed to detect the presence of a received useful HF signal, bywhich a.c. detection means initiates the supply of contactlessactivation information upon the detection of the presence of such auseful HF signal in a detection process, which information enables thecontactless mode to be activated, the circuit in addition includingclock signal detection means connected to a first contact terminal ofthe circuit, which contact terminal is connected to a first transmissioncontact of a data carrier, which clock signal detection means areconstructed to detect the presence of a received clock signal and uponthe detection of the presence of such a clock signal in a detectionprocess enable the supply of contact-bound activation information to beinitiated to indicate activation of the contact-bound mode, and thecircuit includes logic means arranged to receive the contactlessactivation information and the contact-bound activation information andconstructed so as to supply contactless mode-setting informationassociated with said contactless activation information when solely thecontactless activation information occurs and to supply contact-boundmode-setting information associated with said contact-bound activationinformation when solely the contact-bound activation information occursand to give one of the two types of activation information priority overthe other one of these two types of activation information when thesetwo types of activation information occur simultaneously and,accordingly, to supply the mode-setting information associated with theactivation information having priority, the contact-bound mode-settinginformation enabling the contact-bound mode and the contactlessmode-setting information enabling the contactless mode of the circuit tobe set.
 8. A circuit as claimed in claim 7, wherein, if at the same timethe contactless activation information and the contact-bound activationinformation occur, the logic means gives the contact-bound activationinformation priority over the contactless activation information andthey consequently supply the associated contact-bound mode-settinginformation.
 9. A circuit as claimed in claim 7, which has a secondcontact terminal connected to a second transmission contact of a datacarrier, for receiving a first supply potential in the contact-boundmode, wherein the circuit includes supply potential detection meanswhich are connected to the second contact terminal of the circuit, andwhich are constructed to detect the presence of a received first supplypotential and which enable the supply of contact-bound activationinformation to be initiated upon detection of the presence of such afirst supply potential during a detection process.
 10. A circuit asclaimed in claim 9, wherein the supply potential detection means and theclock signal detection means are formed by combination detection meanswhich are arranged to receive the first supply potential for its powersupply and which are constructed both to detect the presence of areceived clock signal and to detect the presence of a received firstsupply potential and wherein the supply of contact-bound activationinformation can be initiated only in the case of a simultaneousdetection of the presence of a clock signal and the presence of a firstsupply potential.
 11. A circuit as claimed in claim 10, wherein thecombination detection means cooperate with memory means capable ofstoring contact-bound activation information supplied during a detectionprocess, and the combination detection means are, in addition, adaptedto also detect the presence of prior contact-bound activationinformation supplied in a previous detection process and stored in thememory means, and the combination detection means maintain the supply ofcontact-bound activation information during a detection process in whichdropping out of a received clock signal but the subsequent presence ofthe first supply potential and the presence of prior contact-boundactivation information are detected.
 12. A circuit as claimed in claim5, characterized in that the memory means are formed by a latch.
 13. Amethod of operation of a data carrier which can be operated in acontact-bound mode and in a contactless mode, comprising the steps of:detecting if the presence of an HF signal providing a usefulcommunications channel is present using an AC signal detector andgenerating contactless activation information if such HF signal ispresent; detecting if the presence of a useful signal is present atleast one contact of the data carrier by detecting the presence of aclock signal on the at least one contact and generating contact-boundactivation information if such HF signal is present; and enablingcontactless communication when solely the contactless activationinformation is present, enabling contact-bound communication when solelycontact-bound information is present and enabling either contactlesscommunication or contact-bound communication depending on a prioritysetting when both contactless activation information and contact-boundinformation are present.